The present invention relates to a shaking grate having inclined continuous tubes disposed parallel to the direction of incline and communicating with a liquid or fluid coolant circuit; the tubes are arranged on a vibrating grate carriage.
German Pat. No. 841,616, and U.S. Pat. No. 2,763,220, describe a tube element of a continuous shaking grate, the grate sheet of which consists of tubes having a coolant flowing therethrough and disposed parallel to one another in the conveying or feeding direction of the fuel. The individual tubes extend continuously from the beginning of the grate to the end of the grate, are inclined to the end of the grate, and covered against the high thermal and mechanical stresses with cast-iron grate bars which space them apart.
The disadvantage of this type of grate is that a heat-conducting paste is introduced between the grate bar and cooling tube for an adequate cooling of the grate bars by the tube, through which coolant flows. This paste must fill the charging chamber in such a way as to be free of gaps, must not lose its effect at temperatures greater than 400.degree. C. during solidification or hardening and by tear or crack formation in changing system operation, and must have sufficient corrosion resistance against physical and chemical attack.
A further disadvantage is the costly construction, fabrication, and assembly. A controlled or regulated distribution of the air for combustion, and a construction of the tubes free of transverse force, is not assured despite the use of calibrated precision steel tubes, for example according to DIN (German Industrial Norm) 2391 despite a high mechanical machining cost of the cast grate bars, and despite considerable care during placement of the dish-shaped, cast-iron grate bars, which are keyed or wedged on.
A similar situation exists for the shaking grates disclosed by U.S. Pat. No. 3,263,655. These shaking grates consist of planar grate sheets which are water cooled, overlap one another, and are assembled in a ladder shape. The tubes which form the crossbars are placed between the side walls of the combustion chamber, while the tubes which form the rungs are covered by grate bars placed and fastened to the underside by means of a strip; such grate bars have openings of T-shaped cross section for the combustion air, and are provided with curvatures adapted to the tube shape.
It is therefore an object of the present invention to develop a shaking grate of the initially described general type which eliminates the cast iron grate covering and uses standard boiler tubes, for example according to DIN 2448, yet is not only simple to construct, fabricate, and assemble, but also ensures a controlled feed and distribution of the air for combustion for the fuel bed which rests on the shaking grate.